Spectral Evolution of an Earth‐like Planet

Abstract

We have developed a characterization of the geological evolution of the\nEarths atmosphere and surface in order to model the observable spectra of an\nEarth-like planet through its geological history. These calculations are\ndesigned to guide the interpretation of an observed spectrum of such a planet\nby future instruments that will characterize exoplanets. Our models focus on\nspectral features that either imply habitability or are required for\nhabitability. These features are generated by H2O, CO2, CH4, O2, O3, N2O, and\nvegetation-like surface albedos. We chose six geological epochs to\ncharacterize. These epochs exhibit a wide range in abundance for these\nmolecules, ranging from a CO2 rich early atmosphere, to a CO2/CH4-rich\natmosphere around 2 billion years ago to a present-day atmosphere. We analyzed\nthe spectra to quantify the strength of each important spectral feature in both\nthe visible and thermal infrared spectral regions, and the resolutions required\nto unambiguously observe the features for each epoch. We find a wide range of\nspectral resolutions required for observing the different features. For\nexample, H2O and O3 can be observed with relatively low resolution, while O2\nand N2O require higher resolution. We also find that the inclusion of clouds in\nour models significantly affects both the strengths and resolutions required to\nobserve all spectral features.\n